SORT

[Takver]

Hi, i'm a total beginner in java. I need a program that reads data from an input file and sort it in a descending order and then outputs it in another output text file. The problem is that the program should not 'know' what data is in the input file. (in the input file there are products and their prices.) How can i do this?
I know how the input and output goes with BufferedReader, PrintWriter and that but i just could not figure out the sorting.
Please help,
Thanks in advance